Global Climate Change Cannot be Predicted

In the summer of 1988 with the thermometer hitting 98 degrees in Washington, D.C., James Hansen, chief of NASA’s Goddard Institute, told a Senate Committee that “the [human caused] greenhouse effect has been detected and it is changing our climate now.” Dr. Hansen said he was “99-percent confident” that current temperature represents a “real warming trend.”

Hansen and other climate experts predicted a catastrophic global warming in the next century if no limits were placed on the emission of carbon dioxide and other greenhouse gases as a byproduct of human activity. Dr. Hansen’s testimony helped to make global warming a major environmental issue and set in motion a series of events culminating in the Kyoto Protocol, which would require the United States and others to reduce drastically their emissions of carbon dioxide.

And now, after ten years, Hansen has taken it all back. In the October 1998 issue of the Proceedings of the National Academy of Sciences he reports that predictions of climate change in the next century are meaningless. According to Hansen and his co-authors, “The forcings that drove long-term climate change are not known with an accuracy sufficient to define future climate change.”

In other words, the natural and manmade influences on global climate – things such as changes in the sun’s brightness, ozone, and clouds and small particles in the atmosphere – are so poorly understood that climate projections for the 21st century are valueless.

Yet these predictions were the driving force behind the Kyoto Agreement.

The Kyoto Agreement on emission limits will have a very destructive impact on the economies of the developed nations which doubtless will, in turn, hurt the economies of developing areas. What is the point to those economically punishing limits on CO2 emissions if we have no idea whether any limiting restrictions are necessary? In the present state of knowledge on the factors controlling climate, according to Hansen, those CO2 limits may be necessary, or they may not be. To act on the basis of meaningless predictions would be irrational.

The bottom line: more research is necessary and time is available to do it. With large resources in money and scientific brainpower already committed to research on the factors controlling climate, we can be confident that in a few years, or five years at most, the climate experts will have a more reliable base for predicting 21st century climate. Several studies have shown that a five-year, or even ten or twenty-year, delay in imposing CO2 limits would have a negligible effect on the global climate in the next century. In view of Hansen’s results, a minimum five-year moratorium on global warming policymaking is the only prudent course.

Partner & Fellow Blogs